ABSTRACT

Technology is one thing that keeps on changing to make life simpler. But, let’s take

the case of charging a device, for decades, we still confine to the old traditional style of wire

system. Think of a device or a system that can charge up multiple systems without all those

snake-look-alike wires. The solution is to go with wireless power transfer using inductive

coupling.

Wireless Power Transmission using inductive coupling, is one of the effective ways

to transfer power between points without the use of conventional wire system. Wireless

power transmission is effective in areas where wire system is unreachable or impossible. The

power is transferred using inductive coupling, resonant induction or electromagnetic wave

transmission depending on whether its short range, mid-range or high range.

The goal of this project Wireless power transmission mobile charger circuit using

inductive coupling is to charge a low power device using wireless power transmission. This

is done using charging a resonant coil from AC and then transmitting subsequent power to

the resistive load. The project is meant to charge a low power device quickly and efficiently

by inductive coupling without the help of wires.

1

Chapter 1

INTRODUCTION

Inductive charging (also known as "wireless charging") uses an electromagnetic

field to transfer energy between two objects. This is usually done with a charging station. Energy

is sent through an inductive coupling to an electrical device, which can then use that energy to

charge batteries or run the device.

Induction chargers typically use an induction coil to create an alternating electromagnetic

field from within a charging base station, and a second induction coil in the portable device takes

power from the electromagnetic field and converts it back into electrical current to charge the

battery. The two induction coils in proximity combine to form an electrical transformer. Greater

distances between sender and receiver coils can be achieved when the inductive charging system

uses resonant inductive coupling. Recent improvements to this resonant system include using a

movable transmission coil ie mounted on an elevating platform or arm, and the use of advanced

materials for the receiver coil made of silver plated copper or sometimes aluminium to minimize

weight and decrease resistance due to the skin effect.

2

Chapter 2

TRANSFORMER

2.1 PRINCIPLE OF THE TRANSFORMER:-

Two coils are wound over a Core such that they are magnetically coupled. The two

coils are known as the primary and secondary windings.

In a Transformer, an iron core is used. The coupling between the coils is source of

making a path for the magnetic flux to link both the coils. A core as in fig.2 is used and the

coils are wound on the limbs of the core. Because of high permeability of iron, the flux path

for the flux is only in the iron and hence the flux links both windings. Hence there is very

little ‘leakage flux’. This term leakage flux denotes the part of the flux, which does not link

both the coils, i.e., when coupling is not perfect. In the high frequency transformers, ferrite

core is used. The transformers may be step-up, step-down, frequency matching, sound

output, amplifier driver etc. The basic principles of all the transformers are same.

Fig.2.1 -Miniature Transformer

3

Fig.2.2-Conventional Power Transformer

4

Chapter 3

POWER SUPPLY

In alternating current the electron flow is alternate, i.e. the electron flow increases to

maximum in one direction, decreases back to zero. It then increases in the other direction and

then decreases to zero again. Direct current flows in one direction only. Rectifier converts

alternating current to flow in one direction only. When the anode of the diode is positive with

respect to its cathode, it is forward biased, allowing current to flow. But when its anode is

negative with respect to the cathode, it is reverse biased and does not allow current to flow.

This unidirectional property of the diode is useful for rectification. A single diode

arranged back-to-back might allow the electrons to flow during positive half cycles only and

suppress the negative half cycles. Double diodes arranged back-to-back might act as full

wave rectifiers as they may allow the electron flow during both positive and negative half

cycles. Four diodes can be arranged to make a full wave bridge rectifier. Different types of

filter circuits are used to smooth out the pulsations in amplitude of the output voltage from a

rectifier.

The property of capacitor to oppose any change in the voltage applied across them by

storing energy in the electric field of the capacitor and of inductors to oppose any change in

the current flowing through them by storing energy in the magnetic field of coil may be

utilized. To remove pulsation of the direct current obtained from the rectifier, different types

of combination of capacitor, inductors and resistors may be also be used to increase to action

of filtering.

3.1 NEED OF POWER SUPPLY

Perhaps all of you are aware that a ‘power supply’ is a primary requirement for the

‘Test Bench’ of a home experimenter’s mini lab. A battery eliminator can eliminate or

replace the batteries of solid-state electronic equipment and the equipment thus can be

operated by 230v A.C. mains instead of the batteries or dry cells. Nowadays, the use of

commercial battery eliminator or power supply unit has become increasingly popular as

power source for household appliances like transreceivers, record player, cassette players,

digital clock etc.

5

3.2 USE OF DIODES IN RECTIFIERS:

Electric energy is available in homes and industries in India, in the form of alternating

voltage. The supply has a voltage of 220V (rms) at a frequency of 50 Hz. In the USA, it is

110V at 60 Hz. For the operation of most of the devices in electronic equipment, a dc voltage

is needed. For instance, a transistor radio requires a dc supply for its operation. Usually, this

supply is provided by dry cells. But sometime we use a battery eliminator in place of dry

cells. The battery eliminator converts the ac voltage into dc voltage and thus eliminates the

need for dry cells. Nowadays, almost all-electronic equipment includes a circuit that converts

ac voltage of mains supply into dc voltage. This part of the equipment is called Power

Supply. In general, at the input of the power supply, there is a power transformer. It is

followed by a diode circuit called Rectifier. The output of the rectifier goes to a smoothing

filter, and then to a voltage regulator circuit. The rectifier circuit is the heart of a power

supply.

3.3 RECTIFICATION

Rectification is a process of rendering an alternating current or voltage into a

unidirectional one. The component used for rectification is called ‘Rectifier’. A rectifier

permits current to flow only during the positive half cycles of the applied AC voltage by

eliminating the negative half cycles or alternations of the applied AC voltage. Thus pulsating

DC is obtained. To obtain smooth DC power, additional filter circuits are required.

A diode can be used as rectifier. There are various types of diodes. But,

semiconductor diodes are very popularly used as rectifiers. A semiconductor diode is a solid-

state device consisting of two elements is being an electron emitter or cathode, the other an

electron collector or anode. Since electrons in a semiconductor diode can flow in one

direction only-from emitter to collector- the diode provides the unilateral conduction

necessary for rectification. Out of the semiconductor diodes, copper oxide and selenium

rectifier are also commonly used.

6

3.4 FULL WAVE RECTIFIER

It is possible to rectify both alternations of the input voltage by using two diodes in

the circuit arrangement. Assume 6.3 V rms (18 V p-p) is applied to the circuit. Assume

further that two equal-valued series-connected resistors R are placed in parallel with the ac

source. The 18 V p-p appears across the two resistors connected between points AC and CB,

and point C is the electrical midpoint between A and B. Hence 9 V p-p appears across each

resistor. At any moment during a cycle of vin, if point A is positive relative to C, point B is

negative relative to C. When A is negative to C, point B is positive relative to C. The

effective voltage in proper time phase which each diode "sees" is in Fig. The voltage applied

to the anode of each diode is equal but opposite in polarity at any given instant.

When A is positive relative to C, the anode of D1 is positive with respect to its

cathode. Hence D1 will conduct but D2 will not. During the second alternation, B is positive

relative to C. The anode of D2 is therefore positive with respect to its cathode, and D2

conducts while D1 is cut off.

There is conduction then by either D1 or D2 during the entire input-voltage cycle.

Since the two diodes have a common-cathode load resistor RL, the output voltage

across RL will result from the alternate conduction of D1 and D2. The output waveform vout

across RL, therefore has no gaps as in the case of the half-wave rectifier.

The output of a full-wave rectifier is also pulsating direct current. In the diagram, the

two equal resistors R across the input voltage are necessary to provide a voltage midpoint C

for circuit connection and zero reference. Note that the load resistor RL is connected from the

cathodes to this center reference point C.

An interesting fact about the output waveform vout is that its peak amplitude is not 9

V as in the case of the half-wave rectifier using the same power source, but is less than 4½ V.

The reason, of course, is that the peak positive voltage of A relative to C is 4½ V, not 9 V,

and part of the 4½ V is lost across R.

7

Though the full wave rectifier fills in the conduction gaps, it delivers less than half

the peak output voltage that results from half-wave rectification.

3.5 BRIDGE RECTIFIER

A more widely used full-wave rectifier circuit is the bridge rectifier. It requires four

diodes instead of two, but avoids the need for a centre-tapped transformer. During the

positive half-cycle of the secondary voltage, diodes D2 and D4 are conducting and diodes D1

and D3 are non-conducting. Therefore, current flows through the secondary winding, diode

D2, load resistor RL and diode D4. During negative half-cycles of the secondary voltage,

diodes D1 and D3 conduct, and the diodes D2 and D4 do not conduct. The current therefore

flows through the secondary winding, diode D1, load resistor RL and diode D3. In both

cases, the current passes through the load resistor in the same direction. Therefore, a

fluctuating, unidirectional voltage is developed across the load.

3.6 FILTRATION

The rectifier circuits we have discussed above deliver an output voltage that always

has the same polarity: but however, this output is not suitable as DC power supply for solid-

state circuits. This is due to the pulsation or ripples of the output voltage. This should be

removed out before the output voltage can be supplied to any circuit. This smoothing is done

by incorporating filter networks. The filter network consists of inductors and capacitors. The

inductors or choke coils are generally connected in series with the rectifier output and the

load. The inductors oppose any change in the magnitude of a current flowing through them

by storing up energy in a magnetic field. An inductor offers very low resistance for DC

whereas; it offers very high resistance to AC. Thus, a series connected choke coil in a

rectifier circuit helps to reduce the pulsations or ripples to a great extent in the output

voltage. The fitter capacitors are usually connected in parallel with the rectifier output and

the load. As, AC can pass through a capacitor but DC cannot, the ripples are thus limited and

the output becomes smoothed. When the voltage across its plates tends to rise, it stores up

energy back into voltage and current. Thus, the fluctuations in the output voltage are reduced

considerable. Filter network circuits may be of two types in general:

8

3.6.1 CHOKE INPUT FILTER

If a choke coil or an inductor is used as the ‘first- components’ in the filter network,

the filter is called ‘choke input filter’. The D.C. along with AC pulsation from the rectifier

circuit at first passes through the choke (L). It opposes the AC pulsations but allows the DC

to pass through it freely. Thus AC pulsations are largely reduced. The further ripples are by

passed through the parallel capacitor C. But, however, a little nipple remains unaffected,

which are considered negligible. This little ripple may be reduced by incorporating a series a

choke input filters.

3.6.2 CAPACITOR INPUT FILTER

If a capacitor is placed before the inductors of a choke-input filter network, the filter

is called capacitor input filter. The D.C. along with AC ripples from the rectifier circuit starts

charging the capacitor C. to about peak value. The AC ripples are then diminished slightly.

Now the capacitor C, discharges through the inductor or choke coil, which opposes the AC

ripples, except the DC. The second capacitor C by passes the further AC ripples. A small

ripple is still present in the output of DC, which may be reduced by adding additional filter

network in series.

9

CIRCUIT DIAGRAM:

Fig:3.1-Full Wave Rectifier

10

Chapter 4

RESISTANCE

Resistance is the opposition of a material to the current. It is measured in Ohms. All

conductors represent a certain amount of resistance, since no conductor is 100% efficient. To

control the electron flow (current) in a predictable manner, we use resistors. Electronic

circuits use calibrated lumped resistance to control the flow of current. Broadly speaking,

resistor can be divided into two groups viz. fixed & adjustable (variable) resistors. In fixed

resistors, the value is fixed & cannot be varied. In variable resistors, the resistance value can

be varied by an adjuster knob. It can be divided into (a) Carbon composition (b) Wire wound

(c) Special type. The most common type of resistors used in our projects is carbon type. The

resistance value is normally indicated by colour bands. Each resistance has four colours, one

of the band on either side will be gold or silver, this is called fourth band and indicates the

tolerance, others three band will give the value of resistance (see table). For example if a

resistor has the following marking on it say red, violet, gold. Comparing these coloured rings

with the colour code, its value is 27000 ohms or 27 kilo ohms and its tolerance is ±5%.

Resistor comes in various sizes (Power rating). The bigger, the size, the more power rating of

1/4 watts. The four colour rings on its body tells us the value of resistor value as given below.

COLOURS CODE

Black-----------------------------------------------------0

Brown----------------------------------------------------1

Red-------------------------------------------------------2

Orange---------------------------------------------------3

Yellow---------------------------------------------------4

Green-----------------------------------------------------5

Blue-------------------------------------------------------6

Violet-----------------------------------------------------7

Grey------------------------------------------------------811

White-----------------------------------------------------9

Fig.4.1-Resistance

The first rings give the first digit. The second ring gives the second digit. The third

ring indicates the number of zeroes to be placed after the digits. The fourth ring gives

tolerance (gold ±5%, silver ± 10%, No colour ± 20%).

In variable resistors, we have the dial type of resistance boxes. There is a knob with a

metal pointer. This presses over brass pieces placed along a circle with some space b/w each

of them.

Resistance coils of different values are connected b/w the gaps. When the knob is

rotated, the pointer also moves over the brass pieces. If a gap is skipped over, its resistance is

included in the circuit. If two gaps are skipped over, the resistances of both together are

included in the circuit and so on.

A dial type of resistance box contains many dials depending upon the range, which it

has to cover. If a resistance box has to read upto 10,000, it will have three dials each having

ten gaps i.e. ten resistance coils each of resistance 10. The third dial will have ten resistances

each of 100.

12

The dial type of resistance boxes is better because the contact resistance in this case is

small & constant.

Chapter 5

CAPACITORS

It is an electronic component whose function is to accumulate charges and then

release it.

Fig.5.1-Capacitors

To understand the concept of capacitance, consider a pair of metal plates which all

are placed near to each other without touching. If a battery is connected to these plates the

positive pole to one and the negative pole to the other, electrons from the battery will be

attracted from the plate connected to the positive terminal of the battery. If the battery is then

disconnected, one plate will be left with an excess of electrons, the other with a shortage, and

a potential or voltage difference will exists between them. These plates will be acting as

capacitors. Capacitors are of two types: -

(1) fixed type like ceramic, polyester, electrolytic capacitors-these names refer to the

material they are made of aluminium foil.

Fig.5.2-Types of Capacitors13

(2) Variable type like gang condenser in radio or trimmer. In fixed type capacitors, it has

two leads and its value is written over its body and variable type has three leads. Unit of

measurement of a capacitor is farad denoted by the symbol F. It is a very big unit of

capacitance. Small unit capacitor are pico-farad denoted by pf (Ipf=1/1000,000,000,000 f)

Above all, in case of electrolytic capacitors, it's two terminal are marked as (-) and (+) so

check it while using capacitors in the circuit in right direction. Mistake can destroy the

capacitor or entire circuit in operational.

14

Chapter 6

TRANSISTOR

The name is transistor derived from ‘transfer resistors’ indicating a solid state

Semiconductor device. In addition to conductor and insulators, there is a third class of

material that exhibits proportion of both. Under some conditions, it acts as an insulator, and

under other conditions it’s a conductor. This phenomenon is called Semi-conducting and

allows a variable control over electron flow. So, the transistor is semi conductor device used

in electronics for amplitude. Transistor has three terminals, one is the collector, one is the

base and other is the emitter, (each lead must be connected in the circuit correctly and only

then the transistor will function). Electrons are emitted via one terminal and collected on

another terminal, while the third terminal acts as a control element. Each transistor has a

number marked on its body. Every number has its own specifications.

There are mainly two types of transistor (i) NPN & (ii) PNP

NPN Transistors:

When a positive voltage is applied to the base, the transistor begins to conduct by

allowing current to flow through the collector to emitter circuit. The relatively small current

flowing through the base circuit causes a much greater current to pass through the emitter /

collector circuit. The phenomenon is called current gain and it is measure in beta.

PNP Transistor:

It also does exactly same thing as above except that it has a negative voltage on its

collector and a positive voltage on its emitter.

15

Fig.6.1-Transistors

Transistor is a combination of semi-conductor elements allowing a controlled current

flow. Germanium and Silicon is the two semi-conductor elements used for making it. There

are two types of transistors such as POINT CONTACT and JUNCTION TRANSISTORS.

Point contact construction is defective so is now out of use. Junction triode transistors are in

many respects analogous to triode electron tube.

A junction transistor can function as an amplifier or oscillator as can a triode tube, but

has the additional advantage of long life, small size, ruggedness and absence of cathode

heating power.

Junction transistors are of two types which can be obtained while manufacturing.

The two types are: -

1) PNP TYPE: This is formed by joining a layer of P type of germanium to an N-P

Junction

Fig.6.2-PNP Junction Transistor

2) NPN TYPE: This is formed by joining a layer of N type germanium to a P-N Junction.

16

P N P

Fig.6.3-NPN junction transistor

Both types are shown in figure, with their symbols for representation. The centre

section is called the base, one of the outside sections-the emitter and the other outside

section-the collector. The direction of the arrowhead gives the direction of the conventional

current with the forward bias on the emitter. The conventional flow is opposite in direction to

the electron flow.

OPERATION OF PNP TRANSISTOR:-

A PNP transistor is made by sand witching two PN germanium or silicon diodes,

placed back to back. The centre of N-type portion is extremely thin in comparison to P

region. The P region of the left is connected to the positive terminal and N-region to the

negative terminal i.e. PN is biased in the forward direction while P region of right is biased

negatively i.e. in the reverse direction as shown in Fig. The P region in the forward biased

circuit is called the emitter and P region on the right, biased negatively is called collector.

The centre is called base.

Fig.6.4:NPN Transistor

17

N P N

The majority carriers (holes) of P region (known as emitter) move to N region as they

are repelled by the positive terminal of battery while the electrons of N region are attracted

by the positive terminal. The holes overcome the barrier and cross the emitter junction into N

region. As the width of base region is extremely thin, two to five percent of holes recombine

with the free electrons of N-region which result in a small base current while the remaining

holes (95% to 98%) reach the collector junction. The collector is biased negatively and the

negative collector voltage aids in sweeping the hole into collector region.

As the P region at the right is biased negatively, a very small current should flow but

the following facts are observed:-

A substantial current flows through it when the emitter junction is biased in a

forward direction.

The current flowing across the collector is slightly less than that of the emitter.

The collector current is a function of emitter current i.e. with the decreaseor

increase in the emitter current a corresponding change in the collector current is

observed.

The facts can be explained as follows:-

1. As already discussed that 2 to 5% of the holes are lost in recombination with the

electron n base region, which result in a small base current and hence the collector

current is slightly less than the emitter current.

2. The collector current increases as the holes reaching the collector junction are

attracted by negative potential applied to the collector.

3. When the emitter current increases, most holes are injected into the base region,

which is attracted by the negative potential of the collector and hence results in increasing

the collector current. In this way emitter is analogous to the control of plate current by small

grid voltage in a vacuum triode.

18

Hence we can say that when the emitter is forward biased and collector is negatively

biased, a substantial current flows in both the circuits. Since a small emitter voltage of about

0.1 to 0.5 volts permits the flow of an appreciable emitter current the input power is very

small. The collector voltage can be as high as 45 volts.

19

Chapter 7

MAKING PRINTED CIRCUIT BOARD (P.C.B.)

7.1 INTRODUCTION

Making a Printed Circuit Board is the first step towards building electronic equipment

by any electronic industry. A number of methods are available for making P.C.B., the

simplest method is of drawing pattern on a copper clad board with acid resistant (etchants)

ink or paint or simple nail polish on a copper clad board and do the etching process for

dissolving the rest of copper pattern in acid liquid.

Fig-7.1-PCB

7.2MATERIAL REQUIRED

The apparatus needs for making a P.C.B. is:-

Copper Clad Sheet

Nail Polish or Paint

Ferric Chloride Powder. (Fecl)

Plastic Tray

20

Tap Water etc.

7.3 PROCEDURE

The first and foremost in the process is to clean all dirt from copper sheet with say

spirit or tri chloro ethylene to remove traces grease or oil etc. and then wash the board under

running tap water. Dry the surface with forced warm air or just leave the board to dry

naturally for some time.

Making of the P.C.B. drawing involves some preliminary consideration such as

thickness of lines/ holes according to the components. Now draw the sketch of P.C.B. design

(tracks, rows, square) as per circuit diagram with the help of nail polish or enamel paint or

any other acid resistant liquid. Dry the point surface in open air, when it is completely dried,

the marked holes in P.C.B. may be drilled using 1Mm drill bits. In case there is any shorting

of lines due to spilling of paint, these may be removed by scraping with a blade or a knife,

after the paint has dried.

After drying, 22-30 grams of ferric chloride in 75 ml of water may be heated to about

60 degree and poured over the P.C.B. , placed with its copper side upwards in a plastic tray

of about 15*20 cm. Stirring the solution helps speedy etching. The dissolution of unwanted

copper would take about 45 minutes. If etching takes longer, the solution may be heated

again and the process repeated. The paint on the pattern can be removed P.C.B. may then be

washed and dried. Put a coat of varnish to retain the shine. Your P.C.B. is ready.

7.4 REACTION

Fecl3 + Cu ----- CuCl3 + Fe

Fecl3 + 3H2O --------- Fe (OH)3 + 3HCL

PRECAUTIONS:

1. Add Ferric Chloride (Fecl3) carefully, without any splashing. Fecl3 is

irritating to the skin and will stain the clothes.

2. Place the board in solution with copper side up.

21

3. Try not to breathe the vapours. Stir the solution by giving see-saw motion to

the dish and solution in it.

4. Occasionally warm if the solution over a heater-not to boiling. After some

time the unshaded parts change their colour continue to etch. Gradually the base

material will become visible. Etch for two minutes more to get a neat pattern.

5. Don't throw away the remaining Fecl3 solution. It can be used again for next

printed Circuit Board P.C.B.

USES:

Printed Circuit Board are used for housing components to make a circuit for

compactness, simplicity of servicing and case of interconnection. Thus we can define the

P.C.B. as : Prinked Circuit Boards is actually a sheet of bakelite (an insulating material) on

the one side of which copper patterns are made with holes and from another side, leads of

electronic components are inserted in the proper holes and soldered to the copper points on

the back. Thus leads of electronic components terminals are joined to make electronic circuit.

In the boards copper cladding is done by pasting thin copper foil on the boards during

curing. The copper on the board is about 2 mm thick and weights an ounce per square foot.

The process of making a Printed Circuit for any application has the following steps

(opted professionally):

Preparing the layout of the track.

Transferring this layout photographically M the copper.

Removing the copper in places which are not needed, by the process of etching

(chemical process)

Drilling holes for components mounting.

PRINTED CIRCUIT BOARD22

Printed circuit boards are used for housing components to make a circuit, for

compactness, simplicity of servicing and ease of interconnection. Single sided, double sided

and double sided with plated-through-hold (PYH) types of p.c boards are common today.

Boards are of two types of material (1) phenolic paper based material (2) Glass epoxy

material. Both materials are available as laminate sheets with copper cladding.

Printed circuit boards have a copper cladding on one or both sides. In both boards,

pasting thin copper foil on the board during curing does this. Boards are prepared in sizes of

1 to 5 meter wide and up to 2 meters long. The thickness of the boards is 1.42 to 1.8mm. The

copper on the boards is about 0.2 thick and weighs and ounce per square foot.

Fig.7.2.-Connections in printed circuit board

Chapter 8

23

PROCEDURE FOR MAKING PROJECT

Building project in the proper manner is really an art, something which must be

prectised and learned through trial and error, it is not all that difficult. The main thing is to

remember to take each step slowly and carefully according to the instructions giving making

since that everything at it should be before proceeding further.

TOOLS: The electronics workbench is an actual place of work with comfortably &

conveniently & should be supplied with compliment of those tools must often use in project

building. Probably the most important device is a soldering tool. Other tool which should be

at the electronic work bench includes a pair of needle nose pliers, diagonal wire cutter, a

small knife, an assortment of screw driver, nut driver, few nuts & bolts, electrical tape,

plucker etc. Diagonal wire cutter will be used to cut away any excess lead length from copper

side of P.C.B. 7 to cut section of the board after the circuit is complete. The needle nose

pliers are most often using to bend wire leads & wrap them in order to form a strong

mechanical connection.

Fig.8.1-Tools used for soldering

MOUNTING & SOLDERING: Soldering is process of joining together two metallic parts.

It is actually a process of function in which an alloy, the solder, with a comparatively low

melting point penetrates the surface of the metal being joined & makes a firm joint between

them on cooling & solidifying.

24

Fig.8.2-Soldering

8.1 THE SOLDERING KIT

1. SOLDERING IRON: As soldering is a process of joining together two

metallic parts, the instrument, which is used, for doing this job is known as soldering Iron.

Thus it is meant for melting the solder and to setup the metal parts being joined. Soldering

Iron is rated according to their wattage, which varies from 10- 200 watts.

2. SOLDER: The raw material used for soldering is solder. It is composition of lead & tin.

The good quality solder (a type of flexible naked wire) is 60% Tin +40% Lead which will

melt between 180 degree to 200 degree C temperature.

3. FLUXES OR SOLDERING PASTE: When the points to solder are heated, an oxide film

forms. This must be removed at once so that solder may get to the surface of the metal parts.

This is done by applying chemical substance called Flux, which boils under the heat of the

iron remove the oxide formation and enable the metal to receive the solder.

4. BLADES OR KNIFE: To clean the surface & leads of components to be soldered is done

by this common instrument.

5. SAND PAPER: The oxide formation may attack at the tip of your soldering iron & create

the problem. To prevent this, clean the tip with the help of sand paper time to time or you

may use blade for doing this job. Apart from all these tools, the working bench for soldering

also includes desoldering pump, wink wire (used for desoldering purpose), file etc.

25

HOW TO SOLDER?

Mount components at their appropriate place; bend the leads slightly outwards to

prevent them from falling out when the board is turned over for soldering. No cut the leads so

that you may solder them easily. Apply a small amount of flux at these components leads

with the help of a screwdriver. Now fix the bit or iron with a small amount of solder and flow

freely at the point and the P.C.B copper track at the same time. A good solder joint will

appear smooth & shiny. If all appear well, you may continue to the next solder connections.

TIPS FOR GOOD SOLDERING

1. Use right type of soldering iron. A small efficient soldering iron (about 10-25 watts

with 1/8 or 1/4 inch tip) is ideal for this work.

2. Keep the hot tip of the soldering iron on a piece of metal so that excess heat is

dissipated.

3. Make sure that connection to the soldered is clean. Wax frayed insulation and other

substances cause poor soldering connection. Clean the leads, wires, tags etc. before

soldering.

4. Use just enough solder to cover the lead to be soldered. Excess solder can cause a

short circuit.

5. Use sufficient heat. This is the essence of good soldering. Apply enough heat to the

component lead. You are not using enough heat, if the solder barely melts and forms a

round ball of rough flaky solder. A good solder joint will look smooth, shining and

spread type. The difference between good & bad soldering is just a few seconds extra

with a hot iron applied firmly.

26

PRECAUTIONS

1. Mount the components at the appropriate places before soldering. Follow the circuit

description and components details, leads identification etc. Do not start soldering before

making it confirm that all the components are mounted at the right place.

2. Do not use a spread solder on the board, it may cause short circuit.

3. Do not sit under the fan while soldering.

4. Position the board so that gravity tends to keep the solder where you want it.

5. Do not over heat the components at the board. Excess heat may damage the components or

board.

6. The board should not vibrate while soldering otherwise you have a dry or a cold joint.

7. Do not put the kit under or over voltage source. Be sure about the voltage either dc or ac

while operating the gadget.

8. Do spare the bare ends of the components leads otherwise it may short circuit with the

other components. To prevent this use sleeves at the component leads or use sleeved wire for

connections.

9. Do not use old dark color solder. It may give dry joint. Be sure that all the joints are clean

and well shiny.

10. Do make loose wire connections especially with cell holder, speaker, probes etc. Put

knots while connections to the circuit board, otherwise it may get loose.

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Chapter 9

DIODE

The simplest semiconductor device is made up of a sandwich of P-type

semiconducting material, with contacts provided to connect the p-and n-type layers to an

external circuit. This is a junction Diode. If the positive terminal of the battery is connected

to the p-type material (cathode) and the negative terminal to the N-type material (Anode), a

large current will flow. This is called forward current or forward biased.

If the connections are reversed, a very little current will flow. This is because under this

condition, the p-type material will accept the electrons from the negative terminal of the

battery and the N-type material will give up its free electrons to the battery, resulting in the

state of electrical equilibrium since the N-type material has no more electrons. Thus there

will be a small current to flow and the diode is called Reverse biased.

Thus the Diode allows direct current to pass only in one direction while blocking it in the

other direction. Power diodes are used in concerting AC into DC. In this, current will flow

freely during the first half cycle (forward biased) and practically not at all during the other

half cycle (reverse biased). This makes the diode an effective rectifier, which convert ac into

pulsating dc. Signal diodes are used in radio circuits for detection. Zener diodes are used in

the circuit to control the voltage.

Fig.9.1-Types of diodes

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Fig.9.2-Power diode and signal diode

Some common diodes are:-

1. Zener diode.

2. Photo diode.

3. Light Emitting diode.

1. ZENER DIODE:-

A zener diode is specially designed junction diode, which can operate continuously

without being damaged in the region of reverse break down voltage. One of the most

important applications of zener diode is the design of constant voltage power supply. The

zener diode is joined in reverse bias to d.c. through a resistance R of suitable value.

2. PHOTO DIODE:-

A photo diode is a junction diode made from photo- sensitive semiconductor or

material. In such a diode, there is a provision to allow the light of suitable frequency to fall

on the p-n junction. It is reverse biased, but the voltage applied is less than the break down

voltage. As the intensity of incident light is increased, current goes on increasing till it

becomes maximum. The maximum current is called saturation current.

3. LIGHT EMITTING DIODE (LED):-

When a junction diode is forward biased, energy is released at the junction diode is

forward biased, energy is released at the junction due to recombination of electrons and

holes. In case of silicon and germanium diodes, the energy released is in infrared region. In

the junction diode made of gallium arsenate or indium phosphide, the energy is released in

visible region. Such a junction diode is called a light emitting diode or LED.

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Chapter 10

6 VOLTS MOTOR CYCLE BATTERY

We have used a motorcycle lead acid battery. This battery is of 6 volts. Power of this

battery is used for glowing tube light when the power supply is off. Otherwise, the power

supply keeps on charging the battery.

NEON LAMP

230 volts neon lamps are connected between 220 volts AC input and transformer.

This lamp is working as an indicator. It indicates whether the power is on or off.

FLUORESCENT TUBE LIGHT

A fluorescent 20 watts tube is used as a source of light. The given circuit operates it

automatically.

Fig.10.1-common battery types

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One can get a constant high-voltage power supply using inexpensive 3-terminal voltage

regulators through some simple techniques described below. Depending upon the current

requirement, a reasonable load regulation can be achieved. Line regulation in all cases is

equal to that of the voltage regulator used.

Though high voltage can be obtained with suitable voltage boost circuitry using ICs

like LM 723, some advantages of the circuits presented below are: simplicity, low cost, and

practically reasonable regulation characteristics. For currents of the order of 1A or less, only

one zener and some resistors and capacitors are needed. For higher currents, one pass

transistor such as ECP055 is needed.

Before developing the final circuits, let us first understand the 3-terminal type

constant voltage regulators. Let us see the schematic in Fig. where 78XX is a 3-terminal

voltage regulator.

Schema

tic for

obtaining low-voltage regulated output using 3-terminal voltage regulators. Rectified and

filtered unregulated voltage is applied at VIN and a constant voltage appears between

pins 2 and 2 of the voltage regulator. *The distribution of two currents in the circuit

(IBIAS and ILOAD) is as shown.

It is highly recommended to use the two capacitors as shown. Electrically

regulator will be at a distance from the rectifier supply. Thus, a tantalum grade

capacitor of 5mf and rated voltage is good. Electrolytic capacitor is not suitable

for it is poor in response to load transients, which have high frequency

components. At the output side a 0.22mf disc ceramic capacitor is useful to

31

eliminate spurious oscillations, which the regulator might break into because of its

internal high gain circuitry.

These voltage regulators have a typical bias current of 5 mA, which is reasonably

constant. By inserting a small resistor Rx between pin 2 and ground, the output

voltage in many cases. By this method voltage increment of 5 to 10 per cent is

practically feasible. However, if a high-value resistance is used to obtain a higher

output voltage, a slight variation in bias current will result in wide variation of the

output voltage.

Now let us see that what can be done to get a higher but constant output voltage.

If to the circuit of Fig. resistor RY and zener Vz are added as shown in Fig., the

output voltage is now given by

VOUT=VR+VZ + IBIAS RX

A constant current flows through RY** because VOUT is constant, and small

variations in IBIAS do not change practically the operating point of Vz. This

situation is like constant current biasing of zener, which results in a very accurate

setting of the zener voltage.

As long a sVIN>VOUT+2 volts, VOZ is constant from the reasoning of Fig,

and thus current through RY is constant.

VOZ=VR + IBIAS Rx

Here the pin 2 of the regulator is raised above ground by Vz + IBIAS Rx. Thus, any

combination of zener with a proper selection of RY can be used.

For example, Let VR=+15 V for 7815

IBIAS=5mA

VZ=39V (standard from ECIL)

For a standard 400mW zener of ECIL make, IZ MAX=10 mA. Thus, if we let pass

5mA through RY to make a 55-volt supply

RY = 55-39=3.2k»3.3k

5 x 10-3

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1

RX = 55-39-15 = 200 ohm

IBIAS 5 x 10-3

Fig.10.2-Schematic for constant high-voltage power supplies

It should be noted here that the maximum input voltage allowed for 78XX regulators

is 35V between pins 1 and 2. We see that the actual voltage betweens pin 1 and 2 of the

regulator in this circuit is

VIN - VZ - IBIAS RX

It is therefore necessary that VIN be so chosen that voltage between pins 1 and 2 of

the IC does not exceed the maximum rating. Also, a high input-output differential voltage

VIN-VOUT means more power dissipation in the series-pass element, the regulator. Thus,

with proper selection of the input transformer voltage and capacitor, this should be

minimized.

For example, if 7805 is used, VR equals + 5V and VZ is 40V, so VOUT=45 volts.

For 7805, the maximum input voltage is 35 V and the minimum 7V. Therefore,

VIN MAX = 45 + 35 - 5 = 75 VOLTS

VIN MIN = 45 + 7 - 5 = 47 VOLTS

Thus, from no-load to full-load condition, the unregulated input voltage-including

peak ripple-should be within these limits. This gives a margin of 75-47, i.e. 28 volt. Hence,

the designer can work out the maximum transformer voltage from the no-load input voltage

chosen on the upper side.

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The capacitor's value can be determined from the full load unregulated voltage

chosen. Roughly, per 100mA current, 100mf capacitor gives 1-volt peak-to-peak ripple.

Hence, capacitor's value can be determined for the desired current.

This circuit will have an excellent load and line regulation. For shot-circuit

protection, it is recommended to use a fast-blow fuse of suitable value. Although the

regulator has inherent short-circuit protection, the maximum current differs from device to

device. Adequate heat sink should be used with the regulator.

Fig10.3-Schematic for constant high-voltage power supplies providing currents in excess of one ampere

Now if currents in excess of 1A are needed, the circuit shown in fig. is useful. This

circuit is similar to that in Fig. except that a pass transistor ECP055 is added besides a 0.5-

ohm or more resistor. This transistor bypasses the excessive current. By selecting proper Rz

the ratio of two currents passing through the regulator and transistor can be altered.

This circuit will show load and live regulation within 1% and will function properly

for VIN-VOUT as low as 4 volt. For short-circuit protection, a fast blow fuse is

recommended as this circuit does not have inherent short-circuit protection. Adequate heat

sink is to be used for the pass transistors. For negative voltages, use 79XX series

regulators and ECN055 as the pass transistor. Some advantages of the circuits described

above are: the lowest cost among comparable performance circuits, ability to work at low

input-output differential, and flexibility in design for various applications.

So audio enthusiasts, if you are troubled by hum emanating from your power

amplifier, try this inexpensive alternative for power supply.

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CHAPTE

R 11

BATTERY CHARGER

Fig.11.1-Battery charger

This unit charges the batteries until they reach a specific voltage and then it trickle

charges the batteries until it is disconnected.

Fig.11.2-Adapter

A simple charger equivalent to a AC-DC wall adapter. It applies 300mA to the

battery at all times, which will damage the battery if left connected too long, a battery

charger is a device used to put energy into a secondary cell or (rechargeable) battery by

forcing an electric current through it.

35

The charge current depends upon the technology and capacity of the battery being

charged. For example, the current that should be applied to recharge a 12 V car battery will

be very different from the current for a mobile phone battery.

10.1 Mobile phone charger

Most mobile phone chargers are not really chargers, only adapters that provide a

power source for the charging circuitry which is almost always contained within the mobile

phone. Mobile phones can usually accept relatively wide range of voltages, as long as it is

sufficiently above the phone battery's voltage. However, if the voltage is too high, it can

damage the phone. Mostly, the voltage is 5 volts or slightly higher, but it can sometimes vary

up to 12 volts when the power source is not loaded.

Battery chargers for mobile phones and other devices are notable in that they come in a wide

variety of DC connector-styles and voltages, most of which are not compatible with other

manufactures' phones or even different models of phones from a single manufacturer.

Users of publicly accessible charging kiosks must be able to cross-reference connectors with

device brands/models and individual charge parameters and thus ensure delivery of the

correct charge for their mobile device. A database-driven system is one solution, and is being

incorporated into some of the latest designs of charging kiosks.

Fig 11.3- ion hub charger

36

The Ion hub charger can simultaneously charge several electronic devices: iPod

Nano, Razr, Nintendo DS Lite, BlackBerry, portable DVD player, and electric shaver.

There are also human-powered chargers sold on the market, which typically consists

of a dynamo powered by a hand crank and extension cords. There are also solar chargers.

China and other countries are making a national standard on mobile phone chargers

using the USB standard.

37

REFERENCES

1. http://www.wikipedia.org

2. http://www.google.com

3. http://www.ablabs.co.in

4. http://www.electronics.com

5. http://www.atmel.com

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